This invention relates generally to a final drive assembly for a crawler tractor and more particularly to a bearing arrangement used in conjunction therewith for rotatably mounting a quill shaft or hub about a nonrotatable sprocket shaft.
In the past, it has been common practice to mount a track driving sprocket on a quill shaft which also mounts a bull gear driven through a gear reduction of the final drive assembly powered by the tractor. The quill shaft is normally supported for rotation about a rigid, nonrotatable sprocket shaft which is mounted in cantilevered relation from a bevel gear and steering clutch case of the tractor.
The present invention is particularly concerned with the problem of adjusting the sprocket hub mounting bearings which has heretofore been accomplished by a relatively large diameter nut which is disposed about the quill shaft between the sprocket and the track frame of the tractor. In practice, the track chain which is wrapped about the sprocket and disposed in closely surrounding relation above, below and to the rear of the nut and the track frame which is disposed in front thereof makes access to the nut for adjustment purposes by the use of a relatively long spanner wrench extremely difficult. The adjustment of the bearing preload is further hindered by the relatively large force necessary to turn the nut due to the relatively large number of components through which the force must be transmitted and the large thread diameter of the nut itself which cause large frictional losses to occur.
For instance, the adjustment nut of a comparable final drive specifies a tightening torque of from 900-1200 ft. lbs (124.47-165.96 kilograms-meters) be applied thereto to provide an axial preloading force on the bearings of approximately 8500-11,000 lbs (3,855.6-4,989.6 kg).
Another problem typically found in prior art bearing mounting configurations is that the bearing cages employed therein are normally fixed in axial relation relative to the sprocket shaft which effects the axial position of the sprocket relative to the track frame and necessitates the use of shims in order to properly align the sprocket with the associated track mounted by such track frame.